Stretchable mechanical/adhesive closure for a disposable diaper

ABSTRACT

A fastening system for releasably securing a diaper provides both mechanical and adhesive or cohesive securement. Tab members comprise a facestock layer, a contact layer of adhesive or cohesive overlying at least a portion of the facestock layer, and mechanical fastening elements projecting from at least a portion of the contact layer. The facestock layer includes extensible and substantially nonextensible polymeric portions. A landing member includes complementary mechanical fastening elements and a contact surface or cohesive for engagement with the tab adhesive or cohesive. A method is also disclosed for making the fastening system.

This application claims the priority of U.S. Provisional Application No.60/010,042, filed Jan. 16, 1996.

BACKGROUND OF THE INVENTION AND RELATED ART

The present invention relates to closures and methods of making closuresfor fastening adjacent portions or edges of materials or componentstogether. The closures are useful as fastening system closures fordisposable diapers.

Diapers of this general type are widely used. A typical diaperconstruction comprises an absorbent pad or batt or the like enclosed inan outer plastic shell or a non-woven backsheet that is non-woven fabriclaminated with a water impermeable layer such as a polyethylene film. Awater permeable inner shell or liner is also provided to promoteseparation of fluid from the user.

The fastener tape system generally includes adhesive tabs fastened toone end of the diaper assembly construction at each lateral side of thediaper in a permanent “factory joint” by the diaper manufacturer usingadhesives or other techniques. The tabs have a face coated withpressure-sensitive adhesive. The tabs are releasably attachable to theother end of the diaper at each lateral side in a “user joint”. Theattachment is releasable both to allow permanent removal of the diaperand to allow unfastening to inspect the diaper followed by refasteningif indicated.

The user joint may be formed by direct connection of the tab to thediaper outer surface whether the latter is formed of a plastic film or anon-woven backsheet. In the case of plastic film shells, it is typicalto provide a “landing zone” formed of reinforcing tape or the like forreceiving the end of the tab to form the user joint. The landing zonemay provide a plastic surface or a non-woven surface and may comprise aknit type fabric landing pad.

The fastener tape system may rely solely upon pressure-sensitiveadhesive in the formation of the user joint as shown in U.S. Pat. Nos.4,795,456, 4,710,190, 4,020,842 and 3,833,456. The use of combinedadhesive and mechanical fastener systems is shown in U.S. Pat. Nos.5,019,065, 5,053,028 and 4,869,724. The teachings of all of thesepatents being incorporated herein by reference.

The use of extensible or stretchable tabs to promote user comfortthrough better fit and more secure mounting is also known in the art.The tabs operate as extensible diaper side waistbands. Examples of suchdiaper fastening systems are disclosed in U.S. Pat. Nos. 4,795,456,4,066,081, 4,051,853 and 3,800,796.

Related art includes U.S. Pat. Nos. 3,464,094, 4,239,829, 5,250,253 andEuropean Publication No. 0 191 355.

SUMMARY OF THE INVENTION

The present invention provides an extensible tab fastener system havinga user joint that enables combined mechanical and adhesive attachment.The mechanical and adhesive attachments each contribute to the totalintegrity or strength of the diaper closure or user joint, and neitherhas to be fully effective to provide the required total closurestrength. The tab fastener system may be produced by high speedmanufacturing processes including coextrusion.

In the illustrated embodiments, the fastening system tab memberscomprise a facestock layer, a contact securement portion comprising alayer of adhesive or cohesive overlying at least a portion of thefacestock layer, and mechanical fastening elements projecting from atleast a portion of the contact layer. The tab contact securement portionextends over at least a portion of the extensible and substantiallynonextensible polymeric portions of the facestock layer. A landingmember includes complementary mechanical fastening elements and contactsecurement portion comprising a contact surface or cohesive forengagement with the tab adhesive or cohesive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a tab fastener of a tab fastener systemin accordance with the invention;

FIG. 2 is a fragmentary perspective view on a reduced scale showing thetab fastener system of FIG. 1 applied to a diaper with the tab in thedeployed position ready for closure;

FIG. 3 is a fragmentary schematic plan view showing the process formaking a tab fastener in accordance with the invention; and

FIG. 4 is a perspective view similar to FIG. 1 showing a tab fastener inaccordance with another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, a diaper tab 10 for use in closure of adiaper 12 is shown. The diaper tab 10 includes a facestock film 14, anadhesive layer 16 and mechanical engagement or fastening elements 18.

The facestock film 14 includes an extensible central polymeric portion14 a and nonextensible terminal or polymeric portions 14 b. Theextensible portion 14 a may be formed of elastomers such as thethermoplastic elastomers sold by the Shell Chemical Company under thedesignations Kraton. These elastomers may be SBS, SIS, SI, S(IS)_(x) andSEBS block copolymers and mixtures thereof. The nonextensible portions14 b of the film 14 may be formed of polypropylene, polyethylene andcombinations of such polymers having suitable film formingcharacteristics.

The adhesive layer 16 may be formed of known adhesive materials such asa pressure-sensitive adhesives including acrylic resin and natural orsynthetic based rubber adhesives. Preferred adhesives include hot meltpressure-sensitive adhesives of the A-B-A block copolymer typecomprising an elastomeric B-block derived from isoprene andthermoplastic A-blocks derived from styrene as disclosed in U.S. Pat.No. 3,932,328. Illustrative rubber based adhesives includestyrene-isoprene-styrene and styrene-butadiene-styrene which mayoptionally contain diblock components such as styrene isoprene andstyrene butadiene. The layer 16 may comprise a cohesive as taught inU.S. Pat. No. 5,085,655 to Mann, which patent is also owned by theassignee herein. The adhesives or cohesives may be applied usinghot-melt, solvent or emulsion techniques. The adhesive or cohesive layer16 may extend along a portion of or substantially all of the adjacentsurface of the layer 14.

The elements 18 are integrally formed with the facestock film 14 in theillustrated embodiment. However, the elements 18 may be separatelyformed and attached to the surface of the facestock. The elements 18extend generally perpendicular from the facestock film 14 and projectthrough the adhesive layer 16. The protuberances provided by theprojecting or exposed ends of the elements 18 should be of sufficientlength to provide mechanical engagement with a locking or engaging arrayof elements, or with a fibrous material such as a non-woven landing tapeor member 20 having fibers 20 a as shown in FIG. 2 or a non-wovenbacksheet of a diaper. Further, the polymer forming the nonextensibleportions 14 b and the elements 18 should be of sufficient stiffness toprovide the required shear strength engagement. It is preferred todispose the elements 18 along only the nonextensible portions 14 b sinceis believed to enhance the shear resistance by limiting tendency of theelements 18 to be laterally displaced.

The pressure-sensitive adhesive is relatively more extensible orstretchable than other adjacent layers, and the tab 10 has overallextensibility characteristics substantially corresponding with thefacestock film 14. That is, the tab 10 includes a central elasticportion 10 a corresponding with the location of the portion 14 a andnonextensible terminal portions 10 b corresponding with the locations ofportions 14 b. As shown, each of the portions 14 a and 14 b extendacross the width of the tab 10 at spaced locations along the length ofthe tab extending between the end portions of the diaper to be joined.

Referring to FIG. 2, one of the terminal portions 10 b of the tab 10 issecured to the diaper 12 at a factory joint at one of the lateral sidesat one end of the diaper 12. The other terminal portion 10 b isdeployable to form a user joint with the landing tape 20 to close thediaper about a wearer such as an infant. It should be appreciated thatthe tab 10 may be provided with nonextensible facestock portionsadjacent each end thereof to facilitate the provision of the factoryjoint with the diaper at one end and the manipulation of the tab to formthe user joint at the other end.

The tab 10 and the landing member 20 provide a fastener system havingboth mechanical and adhesive engagement. During use, the elements 18particularly provide shear strength and the pressure-sensitive adhesivelayer particularly provides tack strength. This may be achieved with theadhesive bond between the pressure-sensitive adhesive layer 16 and thefibrous surface of the landing member 20. If the layer 16 is a cohesive,then the landing member 20 must also include the cohesive as a coatinghaving the fibers 20 a extending therethrough, discrete cohesiveparticles carried by the fibers 20 a or as a separate cohesive area.

Referring to FIG. 3, a coextrusion die 22 extrudes the facestock film 14as a side-by-side coextrusion including adjacent portions 14 a and 14 b.For convenience, the film 14 is shown to include a limited number ofadjacent extensible and nonextensible portions, however, a much largernumber of such portions may be provided along the width or crossdirection of the film 14.

The film 14 upon exiting the die 22 engages a molding-casting roll 24for purposes of further shaping the film. In this instance, the roll 24cooperates with the die to form mechanical engagement elements 18 atleast along the nonextensible portions 14 b. The elements 18 may have avariety shapes such as hooks or mushrooms as are well known in the art.Fibrous hook and loop engagement elements are preferred.

The coextrusion processing requires a matching or near matching of themelt flow characteristics of the plastic materials forming the portions14 a and 14 b. Such matching and processing techniques are known in theart and illustrated, for example, in U.S. Pat. No. 3,800,796.

The adhesive layer 16 is applied to the facestock film 14 along thesurface having the elements 18 extending therefrom. As indicated above,the thickness of the adhesive layer 16 assures a sufficient projectionof the elements 18 to effect mechanical engagement. The adhesive may beapplied at the time of the manufacture of the film 14 or at a later timeand, in either case, known techniques may be used with regulation ofthickness to assure projection of elements 18. An adhesive coating roll26 is shown in FIG. 3 applying the adhesive layer 16 to the film 14.

As shown by the dotted outline in FIG. 3, the film 14 having theadhesive layer 16 applied thereto is subsequently cut in the crossdirection, as by a diaper manufacturer, to provide tabs 10. Each of tabs10 has a central extensible portion 10 a and nonextensible terminalportions 10 b as described above. For convenience of illustration, thefilm 14 is shown to correspond in width with three tabs 10. In practice,the film 14 may have a width corresponding with a much larger number oftabs.

Referring to FIG. 4, a tab 30 includes a facestock layer 32, an adhesivelayer 34 and mechanical engagement elements 36. In the tab 30, aplurality of extensible portions 32 a are provided along the length ofthe tab. As compared with the tab 10, the tab 30 is similarlyextensible, but it does not have a single central extensible portion.Further, the elements 36 in the tab 30 are located along the entiresurface of the adhesive layer 34. However, the elements 36 may bepositioned along only the nonextensible portions 32 b in a similarmanner as in the above described embodiment.

While the invention has been shown and described with respect toparticular embodiments thereof, this is for the purpose of illustrationrather than limitation, and other variations and modifications of thespecific embodiments herein shown and described will be apparent tothose skilled in the art all within the intended spirit and scope of theinvention. Accordingly, the patent is not to be limited in scope andeffect to the specific embodiments herein shown and described nor in anyother way that is inconsistent with the extent to which the progress inthe art has been advanced by the invention.

What is claimed is:
 1. A fastening system for releasably securing adiaper closed about a user includes tab and landing members respectivelymounted to opposite ends of said diaper, each of said tab membersincluding a facestock layer comprising a coextrusion of extensible andsubstantially nonextensible polymeric portions, first contact securementmeans comprising a first contact layer of pressure-sensitive adhesive orcohesive overlying said facestock layer, and first mechanical fasteningelements comprising discrete members extending within and projectingfrom said first contact layer overlying said nonextensible portion ofsaid facestock layer only, said landing member including secondmechanical fastening elements for mechanical interengagement with saidfirst mechanical fastening elements and second contact securement meanscomprising a second contact layer of pressure-sensitive adhesive orcohesive for adhesive or cohesive contact securement with said firstcontact layer, whereby said tab and landing member provide mechanicalinterengagement and simultaneous adhesive or cohesive securement whensaid fastening system secures said diaper about a user.
 2. A fasteningsystem as in claim 1, wherein said first and second mechanical fasteningelements respectively comprise hooks and loops.
 3. A fastening system asin claim 2, wherein said loops also provide said second contactsecurement means.
 4. A fastening system as in claim 1, wherein saidfirst contact layer is a layer of pressure-sensitive adhesive.
 5. Afastening system as in claim 1, wherein said first contact layer is alayer of cohesive.
 6. A fastening system as in claim 5, wherein saidsecond contact layer is a layer of cohesive.
 7. A fastening system as inclaim 1, wherein said landing member comprises a fibrous fabric havingfibers providing said second mechanical fastening elements.
 8. Afastening system as in claim 7, wherein said fibers also provide saidsecond contact securement means.
 9. A fastening system as in claim 1,wherein said discrete members of said first mechanical fasteningelements are formed separate of said first contact layer.
 10. Afastening system as in claim 9, wherein said discrete members of saidfirst mechanical fastening elements are partially embedded in said firstcontact layer.
 11. A method of making a fastening system for releasablysecuring a diaper about a user, said fastening system including tab andlanding members respectively mounted to opposite ends of said diaper,comprising: providing a laminate for forming said tab member bycoextruding a facestock layer including extensible and substantiallynonextensible polymeric portions, applying a first contact layer ofpressure-sensitive adhesive or cohesive over said facestock layer, andproviding first mechanical fastening elements comprising discretemembers extending within and projecting from said first contact layeroverlying said nonextensible portion of said facestock layer only,cutting said laminate to form said tab member with a length and a widthsuch that said polymeric portions extend substantially across the widthof said tab member at spaced locations along the length thereof,providing said landing member including second mechanical fasteningelements for mechanical interengagement with said first mechanicalfastening elements and second contact securement means comprising asecond contact layer of pressure-sensitive adhesive or cohesive foradhesive or cohesive contact securement with said first contact layer,and mounting said tab and landing members to said opposite ends of saiddiaper, whereby said tab and landing member provide mechanicalinterengagement and simultaneous adhesive or cohesive securement whensaid fastening system secures said diaper about a user.
 12. A method asin claim 11, wherein said landing member comprises a fibrous fabrichaving fibers providing said second mechanical fastening elements.
 13. Amethod as in claim 12, wherein said fibers also provide said secondcontact layer and said first contact layer is a layer ofpressure-sensitive adhesive.
 14. A method of as in claim 11, whereinsaid first contact layer has a thickness and an exposed surface remoteof said facestock layer, and providing said first mechanical fasteningelements includes providing said discrete members separate of said firstmechanical fastening elements and attaching said discrete members to thefacestock layer with said discrete members of said first fasteningelements extending through said exposed surface of said first contactlayer.
 15. A method as in claim 11, wherein said first contact layer hasa thickness and an exposed surface remote of said face stock layer, andproviding said first mechanical fastening elements includes integrallyproviding said first mechanical fastening elements and said face stocklayer with said discrete members of said first mechanical fasteningelements extending through said exposed surface of said first contactlayer.